Various articles of manufacture are made with polymer coatings or polymer parts. Such coatings may be used for protective purposes, to protect surfaces from corrosion or abrasion, to add strength to the article or to protect various parts of the article (e.g., electronic circuits) from the effects of atmospheric constituents and for various other purposes.
In the field of optical technology, there is a need for various polymer materials with unique optical and physical characteristics. In particular, there is a need for an encapsulating material (with all the desirable characteristics of encapsulating materials) which also have desirable optical properties such as low loss transmission characteristics and particular indexes of refraction.
A particularly important commercial problem in lightwave technology is the use of polymeric materials as index-matching material for connections between optical components such as between optical fiber and (1) other optical fiber, (2) optical waveguides, (3) optical detectors, (4) light sources, (5) optical lens, etc. Index matching generally requires a polymeric material with an index of refraction close to that of the core of the optical fiber. Index-matching material is required at these interfaces in order to avoid reflection losses due to discontinuities in the refractive index. In addition, it is desirable to have an inexpensive, easily made material that is stable and nontoxic, and has the requisite material characteristics to protect electronic components and optoelectronic components from the deleterious effects of the atmosphere and environment such as humidity, corrosive gases, etc. A particular example of an optoelectronic device requiring protection is a photodetector such as the various PIN photodetectors used in optical communications. Particularly desirable is a encapsulant material which is also useful for index matching one optical component or device to another (e.g. optical fiber to a PIN photodetector).
Silicone resins are used for many purposes because of their relative thermal stability, dielectric properties, chemical stability, low toxicity and resistance to atmospheric deterioration. A good general reference to the chemistry and technology of silicones is given in a book by Walter Noll entitled, "Chemistry and Technology of Silicones", Academic Press, New York, 1968. Silicone resins enjoy a wide variety of uses such as encapsulants and coatings for the electronics industry, sealants and greases, medical implants, and as the media for certain types of touch sensitive displays. In particular, silicone resins in the form of elastomers have been found to provide tough durable protection when used for the encapsulation of integrated circuit (IC) components or devices. Such silicone resins are firm enough to provide protection for fine connections, while flexible enough to allow for the expansion and contraction during ordinary operational temperature cycles. A particular useful review paper on the use of silicone elastomers for IC chip protection is contained in a paper published by C. P. Wong, Materials Research Symposium Proceedings, Vol. 108, pages 175-187 (1988).
U.S. Pat. No. 4,665,148 of C. P. Wong, and its division, U.S. Pat. No. 4,719,274, describe a method of forming a silicone gel by reacting a first silicone polymer having pendant vinyl groups with a second silicone polymer having pendant hydrides. The vinyl groups react with the hydrides, in the presence of a platinum catalyst, to crosslink the polymers into the desired gel.
Various references contain discussions of polymer compositions including organopolysiloxane polymer compositions that are transparent and suitable for various applications to optical technology. U.S. Pat. No. 4,560,711 issued to T. Suzuki on Dec. 24, 1985, discloses various organopolysiloxane compositions. U.S. Pat. No. 3,996,189 and U.S. Pat. No. 4,114,993, both issued to E. A. Travnicek on Dec. 7, 1976 and Sep. 19, 1978 disclose various silicone polymers suitable for optical applications, particularly for contact lenses and intraocular implants. See also, U.S. Pat. No. 3,996,187 issued to E. A. Travnicek on Dec. 7, 1976, where a filed polysiloxane is used to make soft contact lenses.
Vinyl-terminated dimethyldiphenyl siloxane copolymer is available commercially from Huls American, Petrarch Systems Silanes and Silicones, Catalog entitled Silicon Compounds, Register and Review, Bartram Road, Bristol, Pa. 19007, page 281.